Worth CNC & porting 243 heads when using a standard LS6 intake?

[Rhino1]

This is probably more sense check as I sort of know the answer, but is it worth getting stock 243 heads CNC ported with a valve job to flow more than ~260 cfm, when that’s about the flow limit of the LS6 intake?  I’ve got no intention of upgrading the intake later on.

I’m weighing up the options at the moment, as I’ in the UK, so the shipping to & from becomes a factor plus I’ll have to pay tax & duty on the work & shipping as well.

The engine is currently a 5.7 with 241 heads and a XER287HR-12 cam (238/240 0.605/0.609).  I’m planning on changing the cam for one with less overlap to make driving around under 2000 rpm easier, as its a bit of a pain at the moment.

[paul_3rdgen]

I had a similar setup years ago, the ported heads are definitely worth it.  Probably close to 50hp. 


Sent from my iPhone using Tapatalk

[jwvand02]

For what it's worth, when I had almost your exact setup my plan was to just run AFR Enforcer as-cast heads. They were going to be a lot cheaper than sourcing 243 heads and then paying to have them ported. A lot of the power comes from upping the CR anyways.

[Rhino1]

I did look at the enforcer heads but they’re only slightly better than the 243 and I managed to pick up a set of 243’s over here for a good price.

It’s just weighing up getting them ported or not.  It’s looking like the postage would end up nearing the cost of the cnc porting, about $500 for shipping there (£~150) & back (~$320ish).

I was going to up the CR to about 10.8:1ish, with maybe the 0.040 gasket as well.

[Cobranut]

I did look at the enforcer heads but they’re only slightly better than the 243 and I managed to pick up a set of 243’s over here for a good price.

It’s just weighing up getting them ported or not.  It’s looking like the postage would end up nearing the cost of the cnc porting, about $500 for shipping there (£~150) & back (~$320ish).

I was going to up the CR to about 10.8:1ish, with maybe the 0.040 gasket as well.

I'd think you could find someone in the UK who is competent to port a set of heads.

[gnx7]

There has to be a shop in the UK that can do this porting.  Ask on the Facebook groups in your area.

I had an LS1 with AFR205 heads around 10.8:1 compression afterwards and a big 233/239 .650" cam with LS6 intake, ported TB, 1 7/8" long tubes with dual 3" and high flow cats in an FD that made 440rwhp/385rwtq on 91 octane.  That cam was down on power below 4000rpm but above that it was light a light switch had been flipped and it pulled hard to 7100pm.  It was my daily driver and weekend road race car with an 11lb alum flywheel and single disc RAM910 clutch (very aggressive clutch and not easy for people to drive).  In hindsight a smaller cam would've been better and may a bit more compression plus a twin disc. 

There is no reason your heads won't make similar power probably 5-10rwhp less than the AFR's. 

[Rhino1]

Have been meaning to update this but have been either been working on the car or the house!  I did look at who could do this in the UK and it was a mixed bag:

One place could cnc it but didn’t have the flow numbers, and didn’t differentiate between the earlier and later heads.  The CNC work was double what it was is in the states.
One place could CNC it but they’ve have to start from scratch and that would cost.
A few places could do it by hand and flow test it, but not much availability.
Some places would port it by hand but didn’t flow test it as they didn’t think it was required.  They were cheap but didn’t know what I’d be getting.
and some places stated it wasn’t worth doing as the factory ports couldn’t be bettered.

When I originally posted I had postage costs from Katech that were about 3x the cost for me to send to them.  I got a quote with postage from TEA, and their postage costs were comparable to mine, plus I’d also managed to find a cheaper shipping price.

When comparing the cost of the options in the UK to the TEA quote, the UK options were slightly more expensive even when factoring in shipping and take longer.  There are places here that can do it, but it costs more and it’s not their usual work.  Quite a few places advertise the service but no longer provide it.

In the end I sent them to TEA to have them CNC’d with a valve job.  I’ve received them back and installed them on the car a few nights ago, just need to get accessories, damper, intake and radiator back in the car now.  Also, I might take the chance to make the AC lines as I’ve got the car in bits and then mapping it when the weather gets better here.

[Cobranut]

Given all the variables, I think you chose the best option.
Having someone familiar with these engines is worth a lot when it comes to porting. 

[gnx7]

Ported heads on an LS1 with LS6 intake should make around 420-440rwhp depending upon dyno.  My 2800lb FD (LS1/AFR205 heads/LS6 intake/headers/233.239 .600 cam) with 430rwhp went low 11's at 128mph in the 1/4 (100mph in the 1/8).  It was a super fun setup for quite some time.  I yearned for more power quickly so a 427 LS7 was installed making around 530rwhp and went 138mph 1/4 and 109-110mph 1/8.  That made it really fun and while it was a street car I road raced mainly.... it did see the drag strip as well.  In hindsight I would've done a smaller cam as below 4000rpm it was dead and then a light switch flipped at that point up to 7100rpm redline.